were created according to the following description (written from memory, I may have forgotten some detail).

Origins

The Ubuntu image files were made starting from an Ubuntu Xenial 64-bit daily iso file (shortly before the release, more than beta, 'gamma').

The image file of the mini system with text screen was made starting from the Ubuntu Server 16.04 64-bit iso file. A minimal system was created as a starting point for any of the Ubuntu flavours including Ubuntu Server.

Remove or replace the internal drive of the computer you intend to use

This is because it wants to use /dev/sda for the EFI partition.

Boot into the live system

Boot into the live system, but if the target is also a USB pendrive, plug it in before continuing from the grub menu.

Install this Ubuntu system into a drive with at least 16 GB (pendrive, other external drive, or internal drive). Install this text system into a drive with at least 8 GB. If you install to a pendrive it should be a fast pendrive.

If some minor detail goes wrong, you may need to repeat the installation of the bootloaders (trial and error).

gpt-fix

If you clone the compressed iso files, you need to fix the GUID partition table, GPT, because in most cases you clone to another drive size, and GPT is sensitive to that (which is different from the old MSDOS partition table). I made a shellscript file, gpt-fix, that does the work for you. It works for the cases that I have tested. gpt-fix uses gdisk under the hood, and you may need to install it. Run gpt-fix in the directory, where you downloaded it (or install it into a directory in $PATH).

Comments and screenshots

The method described above seems to create a stable system when used in a USB pendrive and also in an SSD connected via eSATA and USB. It is tested in three different laptops, a Toshiba Satellite and an HP Elitebook and a Lenovo X131e and in an ultra-small desktop computer, Intel NUC 6i3SYH, and it has survived such adventures in UEFI and BIOS mode.

It might or might not work to flash the pendrive image directly from a compressed image file to an SSD or HDD drive depending on the sector sizes. The sector size according to parted, 512b/512b, is shown in screenshot #2, in the output from parted.

Ubuntu

Pendrive version

hostname: uefi-n-bios

In BIOS mode:

In UEFI mode:

In the HP computer it boots via eSATA, where it also works when installed according to the description above. It is possible to boot from USB via chainloading. (This HP computer does not want to boot directly from USB if there is a GPT partition table).

HDD/SSD version

hostname: UEFI-n-BIOS

Mini system with 'text' screen user interface

Text mode, main menu:

when Fluxbox is installed, it can be started from here

Installer submenu:

Font submenu:

These screenshots of the text menus are no real screenshots from the console. They were actually made after installing openssh-server and logging in remotely, they are screenshots from 'xterm -fa default -fs 13'.

The partitions and file systems are listed by parted and lsblk in the following code block:

After this cloning operation you should run gpt-fix in order to match the gpt data to the current drive size (unless you are running mkusb version 10.6.6 or newer versions of mkusb, where gpt_zap and gpt_fix are built-in).